Julian B
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| posted on 24/2/04 at 10:39 PM |
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V8 Head upgrade
Can any body tell me what's involved in converting a standard pair of Rover V8 heads into Big valve stage tuned units. I have seen a few
standard heads for sale and wondered if its possible to convert them?
Well thats a simple one then
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Jon Ison
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| posted on 25/2/04 at 08:04 AM |
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with the amount of BTM end grunt that engines got is it worth it ? what heads do you have now? i seem to remember the later SD1 heads have bigger
valves and are said to flow better that the early ones, i have in the garage some where a book about tuning the Rover V8, can dig it out if you wish.
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Julian B
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| posted on 25/2/04 at 08:25 AM |
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Your probably right .
I was offered a pair of heads for £50.00 and i was just wondering if you can do much with them.
I already have the SD1 heads on my engine now, so this might just be a bit of a pipe dream. If you get the chance to hunt that book out i should like
to know what it says.
Cheers
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Jon Ison
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| posted on 25/2/04 at 08:45 AM |
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i have dug the book out.......
ISBN 0-85429-692-1
there is a fair bit about the heads if u want i can u2u my number to you and read the head bits out for you........
bedtime story...........
In a nutshell without spending huge amounts of dosh it seems you have the best heads anyhow, it does say mind you the "vitesse" head is
the best starting point, there is also very little excess material in the ports b4 you break into water ways so be carefull. Fit vitesse valves into
your SD1 heads is about as far as you can go, it says a lot about cam choice too, there is a huge section in back on cams and what each aftermarket
one "should" do. Another point it makes is the "Breathing" of the head only becomes critical at high rpm, in a car as light as
yours it isn't nessacery to drive every where on the rev limiter, a prod on the gass at any revs i would assume will launch you forward pretty
quick, i remember following a V8 powerd 7 on a test some time ago, it was one handfull and he could,nt go thru corners on power like i could, every
corner i left him for dead, by the end of each straight he was there again, BTW i aint knocking the motor by saying that just pointing out with all
that grunt from tickover they can be a "bloody" handfull.
sound great BTW too.
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mackie
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| posted on 25/2/04 at 09:52 AM |
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I'm not sure if the big valve heads use special castings or not bug a good upgrade could be to use vitesse type waisted-stem valves which
improve flow a bit, and a bit of general porting.
It might be fun to get a pair of heads cheap and try and do it yourself, if it all goes wrong you aint lost much but if it works it should be worth a
few bhp.
Another worthy upgrade would be vitesse pistons to up the compression, you might be able to pick some up 2nd-hand, probably quite pricey new since you
need 8!
I'm no expert btw, this is just stuff i've picked up while considering engines and investigating what we need to get it running.
Our starter motor appears to be fooked 
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craig1410
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| posted on 25/2/04 at 01:04 PM |
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Julian,
Dito what has been said on the Vitesse heads but be aware that the Vitesse heads are machined slightly differently to the SD1 heads and the inlet
valves are recessed slightly. This gives some cons as well as pros but nets off to a slight improvement in high valve lift flow which gives better
top-end power.
I'd recommend the David Hardcastle V8 tuning book as it gives lots of advice like this and could save you a few quid in the mid-long term.
If I were you I'd get a pair of Vitesse heads (standard), rebore the engine to the next piston size (+0.010" or 0.020" I think) and
fit Vitesse 9.75:1 pistons. Then get a Weber 500 carb and a decent set of exhaust headers and free-flowing system. The cam is generally fine as
standard or you could get a slightly hotter one. This will probably give close to 240BHP depending on the specifics and will have loads of torque to
go with it.
As for Jon's comments, I can hardly wait!!
Cheers,
Craig.
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Julian B
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| posted on 3/3/04 at 09:19 AM |
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Thanks for the info guys and sorry for not getting back sooner
I managed to pick up a pair of heads from ebayer for £10.50 so i think i will have a go at porting the heads. The guy that had them is building a Dax
Cobra and decided that the rover lump was a bit weedy for his needs............!
I was reading the RPI site and they have a big valve head which costs a stupid £1500
Look Here
Can anyone tell me how to identifiy these heads as the previous owner didnt know what they came from.
Thanks again
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mackie
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| posted on 3/3/04 at 10:50 AM |
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Bargain!
Are there any numbers or codes stamped/cast into them?
You might be able to identify they type by measuring the valve diameters. If you can post that info then it should be possible to identify roughtly
what type they are.
And yes, I guess it is a bit weedy considering that the real thing had an engine with over twice the capacity!
I saw a Dax chassis with a 502ci big block chevy lump in it at Donnington, now that's a big engine! 500 horses in a Cobra must be..
interesting!
[Edited on 3/3/04 by mackie]
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Julian B
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| posted on 3/3/04 at 03:34 PM |
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The only numbers i could see were in the middle of the heads (see blurrey pic) but the valve meaurments were 1.5 and 1.3 inches diameter
Does that mean anything?
The numbers look like casting serial numbers however they are:-
14
birmal
612571
and
3
birmal
602924
b
Cheers again
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mackie
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| posted on 3/3/04 at 03:52 PM |
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Will look in the book later and see.
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craig1410
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| posted on 3/3/04 at 05:31 PM |
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Julian,
Measure the spark plug reach. If they are short plugs then it is a Pre-SD1 head and thus not very good for mod'ing. If they are standard reach
then it is at least an SD1. I think you'd need to extract an Inlet valve to figure out if it is a Vitesse head or not by virtue of having
waisted valve stems just behind the head.
My bet is that they will be SD1 or pre-SD1 non-Vitesse. They can't be later than that as they have the extra row of head bolt holes along the
front edge of each head.
Cheers,
Craig.
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craig1410
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| posted on 4/3/04 at 09:13 AM |
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Julian,
I couldn't remember the exact plug reaches yesterday but the short reach P6B head is 12.7mm (1/2inch) and the standard reach is 19mm (3/4inch).
The valve sizes for a P6B are 38mm and 33mm for inlet and exhaust resp. and the SD1 heads are 40mm and 34mm resp.
HTH,
Craig.
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Julian B
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| posted on 4/3/04 at 09:45 AM |
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Thanks for the info Craig
It looks as if they are the P6B type then but i will go and have another measure in Metric.
Can you just explain what you mean when you say spark plug reach; is that the amount the plug protrudes into the combustion area?
Cheers again all
Julian
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craig1410
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| posted on 4/3/04 at 10:20 PM |
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Julian,
No, the reach is the whole threaded section and the plug shouldn't protrude very far into the combustion chamber at all. Only the last
1/4" or so should protrude and it shouldn't show much(if any) thread inside the chamber (basically just the sparky bit should poke
through!)
If they are P6B heads then I wouldn't recommend using them as the basis for serious time and effort but they will be fine to practice on. I
don't know how many BHP down the P6B heads will be on SD1 heads with all other factors being equal but I'd expect it to be of the order of
5-12BHP. The P6B heads will give good low down power/torque but don't breath as well at higher RPM and this is where "power" peaks.
I know the P6B engine spec states that it produces more power(163BHP) than the SD1 engine(155BHP) but this is due to increased compression
ratio(10.5:1) and would be even higher with SD1 heads.
I agree that commercial cylinder heads can be very expensive and not necessarily good value but if you are patient then a pair of Vitesse heads will
turn up which if reconditioned properly and lightly ported and polished will perform well. Combined with all the right bits in other areas of the
engine including 9.75:1 pistons, Weber 500 carb, Kent 200 camshaft and a good set of big bore (1.75" exhaust headers and free-flowing system.
the engine will be good for 220BHP. If you go to 3.9 litres capacity then you could probably add another 40-50BHP to this figure.
Whatever you do, don't buy commercially modified heads without seeing the results of the flowbench testing, baselined against standard heads.
There are many people out there who will set about heads with a dremel and make it look all shiny and new but won't necessarily improve flow and
may compromise reliability by cutting too close to the water jacket. Also, pay attention to the valve lifts quoted as it is easy to get a standard
head to flow better by doubling the valve lift or removing them altogether!! Some people argue that heads should be tested without valves but I
believe that you should develop heads with the valves installed at the expected maximum lift point as the presence of the valve can significantly
alter the characteristics of the flow and hence alter the grinding requirements.
HTH,
Craig.
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